Thermostatic fuel mixture control



CCL 23, 1952 Y E. P. wlsE 3,059,909

THERMOSTATIC FUEL MIXTURE CONTROL Filed Dec. 9, 1960 2 Sheets-Sheet 1 n wm United States Patent C 3,059,969 THERMSTATIC FUEL MIXTURE CONTRL Eugene P. Wise, Bloomfield Hills, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corpo.

This invention relates to fuel charging systems for automotive engi-nes and in particular to means in such a system, as for example a carburetor for controlling the fuelai-r ratio to the engine in accordance with changes in the ambient atmosphere temperature.

In consequence of changes in the density of atmospheric air from winter to summer, difficulty has long been experienced in providing a comparatively simple fuel charging system for an automotive vehicle that will automatically adapt itself to both summer and winter driving. If the system is set for economical summer driving, then adjustment for fuel enrichment must be made when the ambient temperature falls below approximately 50 F. On the other hand, if the system is set for eiiicient use of high density air during cold winter operation, an excessively rich and wasteful fuel-air ratio will result during summertime driving when the air density drops.

An object of the present invention is therefore to provide a simple economical and highly efficient means in a fuel charging system for an automobile engine to supply 4a comparatively constant fuel-air ratio to the engine regardless of large thermally induced changes in atmospheric air density.

In a customary liquid fuel charging system, a throttle valve in an induction conduit controls the air supply to the engine. A vacuum actuated fuel control mechanism responsive to the pressure in the induction conduit at a location downstream of the throttle valve controls the main fuel iiow to the engine so as to increase said main fuel flow with increasing pressure at said downstream location. Another object of the invention is to provide means responsive to the temperature of the air supplied to the induction conduit for changing the amount of pressure required therein downstream of the throttle valve to actuate the fuel control mechanism `to effect any given rate of fuel iiow, thereby to prevent undesirable leanness of the fuelair mixture when the ambient atmospheric temperature is low and to prevent' excessive enrichment when the ambient temperature is high.

Other and more specic objects are to provide such a mechanism having a restricted pressure transmitting duct connecting the vacuum actuated fuel control mechanism with the induction conduit at a location downstream of the throttle valve to actuate the fuel control mechanism `to increase the fuel supply to the engine with increasing pressure at said location. Also an idle fuel conduit connects a source of idle fuel at atmospheric pressure with a low pressure region of the induction conduit downstream of the throttle valve to supply fuel for engine idling, the idle fuel iiow increasing with decreasing pressure in the idle fuel conduit. The pressure in the idle fuel conduit is biased by means of a restricted biasing conduit connecting the idle -fuel conduit with atmospheric air so as to supply air to the idle fuel conduit and thereby decrease the idle fuel flow that would otherwise exist if it were not for the biasing conduit. A restricted bypass conduit controlled by a thermostatic valve connects the biasing conduit with the pressure transmitting duct. Thus when the bypass conduit is open, a predetermined proportion of the air flow that would otherwise have been directed to the idle fuel conduit to raise the pressure therein is bypassed to the pressure transmitting duct, thereby to raise the pressure in the latter duct and to reduce the pressure 3,il59,99 Patented Get. 23, 1962 in the idle fuel duct. In consequence, the vacuum actuated fuel control mechanism is actuated to increase the main fuel flow to the engine under load and also to increase the idle fuel flow during engine idle conditions. The thermostatic valve means is responsive to the temperature of the air supplied to said induction conduit for opening said bypass conduit at a predetermined low temperature and also to close `the bypass conduit at a predetermined high temperature. Accordingly, for any given pressure at said downstream location, the pressure in the pressure transmitting duct will be higher for low `ambient temperatures than for high ambient temperatures and a desired fuel-air ratio will be predetermined regardless of the ambient temperature. Similarly, the pressure in the idle duct will be lower for low ambient temperatures than for high ambient temperatures and a desired idle fuel supply will be predetermined regardless of the ambient temperature.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary midsectional View through an automobile carburetor embodying the present invention.

FIGURE 2 is a fragmentary diagrammatic enlarged sectional view ysimilar to FIGURE l but taken through the line of centers of one branch of the carburetor induction fuel system including the air vent, idle bleed tube, vacuum actuated stepup plunger and associated stepped needle, and the acceleration fuel pump.

FIGURE 3 is a fragmentary schematic view similar to FIGURE 2, but showing details of the temperature responsive control means for the idle and main fuel systems.

FIGURE 4 is a graphic representation of the fuel-air ratio on the ordinate with respect to the air ow on the abscissa.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring in more particularity to the drawings, a specil-ic example of the present invention is illustrated by way of example in application with a two-barrel automobile carburetor having a body 10 partitioned into two main compartments including a fuel bowl 11 and an air induction conduit 12, reference being hereby made to copending application Serial No. $18,917, filed lune 8, 1959, for a more complete description of the structure and operation of such a carburetor. An upper air horn portion '13 of the carburetor body supplies air to the conduit 12 and is also provided with a cover extension 13a which overlies the fuel bowl. In the case of a two-barrel carburetor as in the present instance, the lower portion of the conduit 12 ybifurcates into two parallel branches 12a connected by separate manifolds with the engine cylinders for supplying fuel and air thereto. A lower throttle body portion 14 of the carburetor is provided with parallel induction conduits which communicate with the downstream openings of the two branches 12a to comprise continuations thereof. Gaskets 15 and 16 space the central body portion of the carburetor from the upper air horn portion 13 and lower throttle body portion 14 respectively.

The fuel chamber 11 and induction conduit system 12 are separated by a wall l17 having a recessed upper portion providing a horizontal shelf or platform 13. 'I'he latter supports a venturi assembly including a pair of small venturis 19, one associated with each branch 12a of the induction conduit and opening into the upper region of a large venturi 19a formed in the associated induction -branch 12a immediately above the throttle body 14. The paired small venturis 19l are supported by an extension 20 which overlies and is suitably secured to the platform 18, being spaced therefrom by a gasket 21. In the present instance the extension 2G comprises two parts including an upper portion `20a supported and spaced from the lower portion by a suitable gasket 22.

A tubular fuel inlet fitting 23 connected with a suitable source of pressurized fuel screws into the side wall of the bowl 11 to supply fuel thereto under the control of a customary iloat regulated valve 24. An acceleration fuel pump cylinder 25 is provided in bowl 11 in association with a vertically reciprocable plunger 26, which is operably connected with the fuel throttle so that when the latter is released, the plunger 26 and attached piston -27 are raised against the tension of spring 28, thereby to draw fuel into the lower portion of the cylinder 25 via conduit 29 and one-way check ball valve 30. In the event that the accelerator is depressed in a call for additional fuel, plunger 26 is released to enable spring 28 to force piston 27 down, thereby to force fuel from cylinder 25 through acceleration fuel supply conduit 31, formed partially in body and extension 20, and thence into acceleration jet orifice 32 which opens from extension into conduit 12 at a location between and adjacent the upper ends of the venturis 19.

A one-way check ball valve 33 prevents return flow of fuel in the line 31. Also a vent port 34 intersecting orifice 32 and in communication with vent conduit 35, which extends through portions of the body 10 and air horn 13, prevents a syphon action through conduits 31 and 29. Vent conduit 35 opens into an upper portion of conduit 12 near the top of the air horn 13. The latter is provided with an annular boss 36 for attachment to an air lter whereby filtered air is supplied to conduit 12. Also the air horn portion of conduit 12 carries the usual vacuum and thermostatically controlled choke valve 37 mounted on a transverse pivot shaft 38 journalled at opposite ends in the air horn 13. Similarly, each of the induction conduit portions 12a in the throttle body 14 is provided with a throttle valve 39 secured to a common pivotal shaft 40 journalled in the throttle body 14.

In the present instance, each venturi 19 is associated with an independent main fuel supply, each similar to the other so that only one is described herein. As illustrated in FIGURE 2, each main fuel supply comprises a plurality of radially extending ports 41 opening from the bowl 11 into the interior of a vertically extending tubular guide member 42 which screws into a threaded bore in the base of bowl 11. A portion of the bore of the guide member 42 downstream of the ports 41 is restricted at 43 to provide a metering orice which opens into a fuel supply conduit 44 in communication with the bottom of a fuel well `45. The latter is formed in the extensions 26 and 20a and in the wall 17 at the region of the platform 18 and contains a vertically extending `vent tube 46 and idle lbleed tube `47 secured at their upper ends within the extension portion 20a. The upper end of vent tube 46 is vented at 48 to the interior of induction conduit 12 at a location above the venturis 19 and is provided with a plurality of longitudinally spaced air discharge ports 4-9 opening into the well 45. The upper portion of well 45 is in communication with the interior of induction conduit '12 via a fuel supply conduit 50 formed partially in each of the extension portions 20 and 20a and terminating in a nozzle 51 which discharges into one of the small venturis 19.

In accordance with the structure described, the discharge end of-nozzle 51 is subject to the volume of air i ilow through its associated venturi 19 so as to draw fuel from well with increasing force as throttle valve 39 is progressively opened. In this action air is drawn through vent 48 and discharged into well 45 through the ports 49 to aerate the fuel within the well and to facilitate its ilow toward nozzle 51.

In order to obtain fuel enrichment during operation of the engine at high load, as for example during acceleration, metering orifice 43 is controlled by a stepped rod or needle valve 52 registering coaxially with orifice 43, FIGURE 2, and having a lower end 53 of reduced cross sectional area. The upper end of rod 52 is secured to a cross arm 54 which in turn is secured to the upper end of a vacuum actuated plunger 55 slidable vertically within a tubular bore 56 formed in the body 10. An enlarged upper portion of the bore 56- provides an annular seat or shoulder 57. A reduced upper portion of the plunger 55 provides an annular shoulder 58 on which is seated a vertically slidable annular washer 59. The latter extends into the annular enlargement of bore 56 above the `seat '57 and is adapted to seat thereon upon downward movement of plunger 5S as described below. A coil spring 60' around the upper end of plunger 55 and under compression between cross arm 54 and washer 59 urges the latter downwardly against the seat 58. A second coil spring 61 under compression between the bottom of bore 56 and plunger 55 yieldingly urges the latter upwardly.

Vacuum actuation of plunger 55 is accomplished by means of a pressure conducting duct 62. extending through portions of the bodies 19 and 14 and communicating with one of the conduit portions 12a downstream of the associated throttle valve 39, FlGURE l. A restriction 62a in duct 62 enables control of the low pressure induced in chamber 56 at the underside of plunger 55 in response to low pressure downstream of throttle valve 39. An upper portion of the plunger 55 is provided with an outer annular groove 63 vented to atmospheric pressure at the upper portion of the fuel bowl by means of a duct 64 so as to prevent fuel from being drawn downwardly around the washer 59 and into the low pressure of chamber 56 below plunger 55.

The idle fuel system includes a restricted idle fuel supply port 65 opening into tube 47 adjacent the bottom of well 45. The upper end of tube 47 is provided with a radial port 66 in communication with duct 67 formed in extension 26a and communicating with an annular groove 63 extending around the outer periphery of the shank of a tubular screw 69. The latter extends downwardly through extensions 26 and 26a and screws into the platform 18 to secure the latter and extensions Zi) and 2da securely together. A plurality of radial ports l' extend from groove 68 to a restricted air vent duct 71 formed coaxially in screw 63 and opening at the top o-f the latter into the upper portion of conduit 12. The lower end of duct 71 communicates with a bore 72 extending coaxially downward through screw 69 and communicating with an idle bleed duct 73 formed in the bodies 10 and 14 and opening at 74 into the associated conduit portion 12a downstream of the throttle valve 39. Adjustment of the idle `fuel may be accomplished by means of a conventional idle adjustment screw and valve assembly 75 adjustable to vary the restriction of port 74.

IDuring t-he usual operation of the engine at idle conditions when throttle valve 39 is closed, a comparatively high vacuum exists at port '74, whereby fuel for supplying the engine requirement at idle conditions is sucked through conduits 72 and 73 from idle bleed tube 47 via port 66 and ducts 67 and 70. Atomizing air for the idle fuel is supplied by the restricted vent duct 71. A limited amount of atomizing air is also supplied to conduit 73 via pressure biasing duct 76, FIGURE 3, in communication with chamber 77 `formed in the lower portion of body 10 at a location immediately above gasket 16 and between the induction conduitportions 12a. The chamber 77 is closely associated thermally with the air flow in conduits ma by proximity thereto, so as to be responsive to the temperature of the carburetor air flow to the engine, but is sealed frori direct communication with said air flow by means of gasket 16. In -this regard, gasket i6 also serves as a heat dam to shield chamber 77 from the direct heat of the engine on which the carburetor is mounted. Chamber 77 is in communication with vent conduit 35 via a biasing duct 78 restricted at 78a. By reason of the air ow through restriction 78a into chamber 77, the pressure in the latter and correspondingly in conduit 73 is biased at a higher value than would otherwise exist if it were not for such air flow. Restriction 78a is predetermined with respect to the remainder of the fuel system, including vent duct 71 and the adjustahly restricted idle fuel discharge port 74, so as to supply the desired fuel-air mixture for engine idling during the customary warm summer time ambient atmcspheric air conditions.

Also during idle conditions, the low pressure downstream of valve 39 is conducted via restricted conduit 62 into chamber 56 at the underside of plunger 55. The resulting low pressure below plunger 55 rforces the latter downwardly, causing washer 59 to seat at 57 and compressing both springs et) and 61 until the large diameter portion of rod 52 is moved into metering orifice 43 to effect optimum restriction thereof. Inasmuch as practically no air is flowing through the venturis 19, no appreciable fuel will be discharge from nozzles Si.

When throttle valve 39 is partially open, as for example during operation of the engine under steady state cruising conditions, the air liow through each small venturi 19 will be increased to draw fuel through the associated orifice 43 into conduit 44, well 45, and thence via conduit 50 to nozzle 51. During this state of operation, the low pressure downstream of valve 39 is still sufficient to compress both springs 60 and 61 and to maintain tne large diameter portion of rod 52 within orifice 43. The condition of the fuel-air ratio supplied to the engine throughout the cruise range is illustrated by the solid line 79 of FIGURE 4.

As the engine load is increased and throttle Valve 39 is progressively opened, as for example during moderate acceleration, the pressure downstream of valve 39 is increased to enable springs 60 and 61 to force plunger 55 upwardly until only the reduced diameter portion 53 extends within the metering orifice 43. During this condition of operation which is illustrated in FIGURE 4 by a solid line 80 representing the fuel-air ratio supplied to the engine during conditions of partial acceleration, washer 59 moves above shoulder 57 and carries the force of spring 6ft.

Finally when the throttle is in the wide open condition for full engine load, the maximum pressure is attained downstream of valve 39 and spring 61 is enabled Ito move plunger 55 upwardly until the restricted portion 53 is withdrawn completely from orifice 43, as illustrated in FIGURE 2. The fuel-air ratio during this condition of operation is represented by solid 'line 81 of FIGURE 4.

The two springs 60 and 6l are employed to give the desired non-linear spring reaction to the vacuum force acting on plunger 55. The latter force drops ofi? sharply from the idle condition as the throttle valve 39 first opens, then drops off more gradually as the throttle valve 39 continues to open. During engine operation at high vacuum downstream of valve 39, the annular washer 59 seats at 57 to cause compression of spring 60 approximately concurrently with movement of the large diameter portion of rod 52 into the metering port 43.

In order to prevent objectionable leanness of the fuelair mixture during winter driving conditions when the air density is high, and to prevent excessive enrichment of the fuel-air mixture during summertime driving when the air density is low, a bimetallic thermostat element 82 is secured to the body 10 within the chamber or recess 77 by means of screws 83. A bypass bleed duct 84 in body 10 connects chamber 77 with the pressure conducting duct 62. Duct 84 opens into chamber 77 at `a restricted metering orifice 84a. A tapered valve 85 connected with the free end of thermostatic element` 82 for operation thereby registers with the orifice 84a tto close the latter when the engine is operating under con ditions of comparatively warm ambient atmospheric air temperature.

Assuming now that the carburetor with duct 84 closed is adjusted for optimum efficiency of yoperation during summertime operation, the dotted lines 86 and 87 in FIGURE 4 illustrate the effect of suddenly opening valve 85 so as to establish communication between conduit 62 and the higher pressure of recess 77 without regard to the iambient temperature. Upon -openiug valve 85, lair pressure from recess 77 immediately raises the pressure in conduit 62 vand in bore 56 below plunger 55 by reason of the restriction 62a. Accordingly for any given low pressure downstream of throttle valve 39, the vacuum force urging plunger 55 downwardly will be decreased in -comparison to the vacuum force acting on the plunger when duct 84 is closed by valve l85.

Restriction 62a is dimensioned so that when duct 84 is closed and the throttle valve 39 is partially open in the crui-se range represented by line 79, if duct 84 is then opened without regard to temperature conditions, the resulting increased pressure in chamber 56 below plunger 55 would enable springs 60 and 61 to raise plunger 52 until only the reduced portion 53 extends within metering orifice 43, thereby to enrich the -fuelair mixture substantially las indicated by dotted line 86. Similarly if duct 84 is opened without regard to temperature when throttle valve 39 is adjusted for the part acceleration condition represented by line 80, the reduced pressure in chamber 56 below plunger 55 will enable spring 61 to raise rod 52 until the reduced end 53 is withdrawn completely from orifice 43, thereby to enrich the fuel-air mixture substantially to the value indicated by dotted line 87.

It is to be emphasized, however, that valve is thermostatically controlled and opens only at a low temperature when the density of the ambient air is correspondingly high. Accordingly the increased fuel flow resulting from opening of valve 85 during norm-al operation will cor-respond to the increased air -density and result in ra substantially desired uniform fuel-air ratio indicated by the solid lines 79, 80, and 81.

In practice, the valve 85 progressively opens with decreasing temperature when the ambient lair temperature drops below about 50 F. and is completely open when the ambient air temperature is approximately 20 F., so fas to enable Ka substantially uniform fuel-air ratio in the -fuel supplied to the engine throughout the normally encountered range of variations in the ambient air temperature. The thermostatic element 82 is located in the present instance in the body 10 both for convenience of location and because of its proximity to the engine air supply which -at the region of the recess 77 4is closely related to the ambient air temperature. It will be -apparent, however, that the temperature sensing means for valve 85 could be located in any convenient location responsive to the temperature of the ambient air entering the upper end of conduit 12.

Also as valve 85 progressively opens orifice 84a in consequence of progressively colder lambient air temperatures, the air flow to conduit 73 via duct 76 is progressively decreased by reason of the bypass effect of duct 84 which diverts a portion of the 'air flow from chamber 77 to conduit 62. Accordingly the pressure in conduit 73 progressively falls with `decreasing ambient temperature as valve 85 gradually opens the bypass conduit 84, whereby the idle fuel flow into conduit 73 and thence through port 74 into the induction conduit is progressively enriched as desired with decreasing `ambient temperature. In the above regard, the restriction at orifice 84a is determined with respect to the remainder of the fuel system, including restrictions `62a and 78a, so as to proportion the lair flow suitably in conduits 76 and 84, there-by to eect the desired cold weather pressure reduction in conduit '73 during engine idling and the desired cold weather pressure increase 1n conduit 62 during cruise and part acceleration conditions.

I claim:

1. In -a fuel charging system for an internal combustion engine having conduit means for supplying air to said engine, throttle valve means for controlling the air flow in said conduit means, primary fuel supply means for supplying fuel to said engine, pressure actuated means cooperable with said fuel supply means for controlling thc fuel supply to said engine, pressure con-I ducting means connecting the pressure `of said conduit means fat a location downstream of said throttle valve `means with said pressure actuated means to actuate the latter to increase the fuel -supply to said engine with increasing pressure at said location, idle fuel supply means including lan idle fuel duct ldischarging into said yconduit means downstream of said throttle valve means to supply fuel to said engine during idling thereof, pressure biasing duct means connecting said idle fuel duct with a source of air pressure equal to the pressure in said conduit means upstream of said throttle valve means to discharge air into said idle fuel duct from said source, bypass duct means connecting said pressure conducting means with said pressure biasing duct lmeans to divert a portion of the Iair iiow in the latter duct means from said idle fuel duct to said pressure conducting means when said bypass duct means is open, thereby to increase the pressure in said pressure conducting means and to decrease the pressure in said idle fuel duct when said bypass duct means is open, `and means responsive to the temperature of the air supplied to said conduit means and coopera-ble with Said bypass duct means to close the latter `when .said temperature is above a predetermined value.

2. In a fuel charging system for an internal combustion engine having conduit means for supplying air to said engine, throttle valve means for controlling the air ow in said conduit means, primary fuel supply means for supplying fuel to said engine, pressure actuated means cooperable with said fuel supply means for controlling the fuel supply to said engine, pressure conducting means connecting the pressure `of said conduit means at a location downstream of said throttle valve means with said pressure actuated means to actuate the latter to increase the fuel supply to said engine with increasing pressure at said location, idle fuel supply means including an idle fuel duct discharging into said conduit means downstream of said throttle valve means to supply fuel to said engine during idling thereof, pressure biasing duct means connecting said idle fuel duct with a source of air pressure equal to the pressure in said conduit means upstream of said throttle valve means to discharge air intor said idle fuel duct `from said source, bypass duct means connecting said pressure conducting means with said pressure biasing duct means to divert la portion of the iair flow in the latter duct means from said idle fuel duct to said pressure conducting means when said bypass duct means is open, thereby to increase the pressure in said pressure conducting means and to decrease the pressure in said lidle fuel duct when said bypass duct means is open, and means responsive to the temperature of the lair supplied to said conduit means and cooperable with said bypass duct means to close the latter progressively with increasing temperature above a predetermined value.

3. 'In a fuel charging system for lan internal combustion engine having conduit means for supplying air to said engine, a throttle valve for controlling the air ow in |said conduit means, fuel supply means for supplying fuel to said engine, fa reciprooable pressure actuated member `operably connected with said fuel supply means for decreasing the fuel supply to said `engine upon movement of said member in one direction, means yieldingly urging said member in the opposite direction to increase said fuel supply, means for connecting one side of said member with the pressure of said conduit means at -a location `downstream of said throttle valve to move said member in said one direction with increasing force as the pressure at said location decreases, idle fuel supply means including an idle fuel duct discharging into said conduit means downstream of said throttle valve to supply fuel to s-aid engine during idling thereof, pressure biasing duct means connecting said idle fuel duct with a source of -air pressure equal to the pressure in said conduit means upstream of said throttle valve to discharge lair into said idle fuel duct from said source, bypass duct means connecting said one side of said member with said pressure biasing duct means to direct =a portion of the yair ow in the latter duct me-ans from said idle fuel duct to said one side when said bypass duct means is open, thereby to increase the pressure at said one side and to `decrease the pressure in said idle fuel duct when said bypass duct means .is open, and temperature responsive means -cooperable with said bypass duct means and responsive to the temperature of the yair supplied to said conduit means to progressively restrict said bypass duct means with increasing temperature.

4. In a carburetor for an internal combustion engine having induction conduit means for supplying 1air to said engine, said carburetor including a main body having a portion of said induction conduit means extending therethrough, a throttle body secured to s-aid main 'body at the downstream end of said induction conduit portion and having a second portion of said induction conduit extending therethrough and comprising a continuation of the first-named conduit portion, a throttle valve carried by said throttle body for controlling the air flow in said conduit means, fuel supply means for supplying fuel to said engine, a reciprocable pressure actuated member operably connected with said fuel supply means for decreasing the fuel supply to said engine upon movement of said member in one direction, means yieldingly urging said member in the opposite direction to increase said fuel supply, means for connecting one side of said member with the pressure of said conduit means at a location downstream of said throttle valve to move said member in said one direction with increasing force as the pressure at said location decreases, idle fuel supply means including a restricted idle fuel duct discharging into said conduit means downstream of said throttle valve to supply fuel to said engine during idling thereof, restricted pressure biasing duct means connecting said idle fuel duct with a source of air pressure equal to the pressure in said conduit means upstream of said throttle valve to discharge air into said idle fuel duct from said source, restricted bypass duct means connecting said one side of said member with said pressure biasing duct means to direct a portion of the air flow in the latter duct means from said idle fuel duct to said one side when said bypass duct means is open, thereby to increase the pressure at said one side and to decrease the pressure in said idle fuel duct when said bypass duct means is open, and temperature responsive means cooperable with said bypass duct means `and responsive to the temperature of the air supplied to said conduit means to progressively restrict said bypass duct means with increasing temperature.

5. In a fuel charging system for an internal combustion engine having an induction conduit for supplying air to said engine, a throttle valve in said induction conduit for controlling the air ow therein, means for supplying liquid fuel to said engine including a primary fuel metering orifice, a metering plunger registering with said orice, said plunger being movable into or out of said orifice to decrease or increase the fuel supply to said engine respectively, pressure actuated means operably connected with said plunger to move the latter into or out of said orice, pressure conducting means connecting the pressure of said induction conduit downstream of said throttle valve with said pressure actuating means to actuate the latter to move said plunger out of said orifice with increasing pressure, idle fuel supply means including an idle fuel duct having a restricted outlet discharging into said induction conduit downstream of said throttle valve to supply fuel to said engine during idling thereof, restricted pressure biasing duct means connecting said idle fuel duct with a source of air at a pressure greater than the pressure in said induction conduit downstream of said throttle valve during engine idling, thereby to discharge air into said idle fuel duct from said source, restricted bypass air duct means connecting said pressure conducting means -with said pressure biasing duct means to divert a portion of the air flow in the latter duct means from said idle fuel duct to said pressure conducting means when said bypass duct means is open, thereby to increase the pressure in said pressure conducting means and to decrease the pressure in said idle fuel duct when said bypass duct means is open, and means responsive to the temperature of the air supplied to said induction conduit and cooperable with said bypass duct means to restrict the latter with increasing temperature.

6. In a fuel charging system for an automotive internal combustion engine having an induction conduit for supplying air to said engine, a throttle valve in said induction conduit for controlling the air flow therein, means for supplying the primary fuel to said engine, -fuel control means associated with the last-named means for controlling the primary fuel supply to said engine to effect a substantially predetermined cruise fuel-air ratio at steady cruise conditions, a substantially predetermined intermediate yfuel-air ratio at intermediate conditions of acceleration, and a substantially predetermined load fuel-air ratio at approximately wide open throttle conditions, said fuel control means including pressure actuated means connected with the air pressure in said induction conduit downstream of said throttle valve to decrease the fuel supply to said engine as said air pressure decreases, idle fuel supply means including an idle fuel duct having a restricted outlet discharging into said induction conduit downstream of said throttle valve to supply fuel to said engine during idling thereof, restricted pressure biasing duct means connecting said idle fuel duct with a source of air at a pressure greater than the pressure in said induction conduit downstream of said throttle valve during engine idling, thereby to discharge air into said idle lfuel duct from said source, means for increasing the idle fuel supply and also the primary fuel supply to said engine for any given pressure downstream of said throttle valve so as to increase the fuel-air ratio to approximately said intermediate fuel-air ratio at said moderate conditions of acceleration and to approximately said load fuel-air ratio at said intermediate conditions of acceleration, the last-named means comprising a restricted bypass air duct means connecting said pressure actuated means with said pressure biasing duct means to divert a portion of the air flow in the latter duct means from said idle fuel duct to said pressure actuated means when said bypass duct :means is open, thereby to increase the pressure at said pressure actuating means and to decrease the pressure in said idle fuel duct when said bypass duct means is open, and means for controlling the restriction of said bypass duct means.

7. In a fuel charging system for an automotive internal combustion engine having an induction conduit for supplying air to said engine, a throttle valve in said induction conduit for controlling the air flow therein, means for supplying the primary fuel to said engine, fuel control means associated with the last-named means for controlling the primary fuel supply to said engine to effect a substantially predetermined cruise fuel-air ratio at steady cruise conditions, a substantially predetermined intermediate fuel-air ratio at intermediate conditions of acceleration, and a substantially predetermined load fuelair ratio at approximately wide open throttle conditions, said fuel control means including pressure actuated means connected with the air pressure in said induction conduit downstream of said throttle valve to decrease the fuel supply to said engine as said air pressure decreases, idle fuel supply means including an idle fuel duct having a restricted outlet discharging into said induction conduit downstream of said throttle valve to supply fuel to said engine during idling thereof, restricted pressure biasing duct means connecting said idle fuel yduct with a Source of air at a pressure greater than the pressure in said induction conduit downstream of said throttle valve during engine idling, thereby to discharge air into said idle fuel duct from said source, means for increasing the idle fuel supply and also the primary fuel supply to said engine for any given pressure downstream of said throttle valve so as to increase the fuel-air ratio to approximately said intermediate fuel-air ratio at said moderate conditions of acceleration and to approximately said load fuel-air ratio at said intermediate conditions of acceleration, the lastnamed means comprising a restricted bypass air duct means connecting said pressure actuated means with said pressure biasing duct means to divert a portion of the air ow in the latter duct means from said idle fuel duct to said pressure actuated means when said bypass duct means is open, thereby to increase the pressure at said pressure actuating means and to decrease the pressure in said idle fuel duct `when said bypass duct means is open, valve means normally closing said bypass duct means, and means responsive to the temperature of the air supplied to said induction conduit and cooperable with said valve means to open the latter when said temperature falls to a predetermined low value.

8. In a fuel charging system for an internal combustion engine having conduit means for supplying air to said engine, throttle `valve means for controlling the air flow in said conduit means, primary fuel supply means for supplying fuel to said engine, pressure actuated means cooperable with said fuel supply means for controlling the fuel supply to said engine, pressure conducting means connecting the pressure of said conduit means at a location downstream of said throttle valve means with said pressure actuated 4means to actuate the latter to increase the fuel supply to said engine with increasing pressure at said location, idle fuel supply means including an idle fuel duct ldischarging, into said conduit means downstream of said throttle valve means to supply fuel to said engine during idling thereof, pressure biasing duct means connecting said idle fuel duct with a source of air pressure equal to the pressure in said conduit means upstream of said throttle valve means to discharge air into said idle fuel duct from said source, bypass duct means connecting said pressure conducting means `with said pressure biasing duct means to divert a portion of the air flow in the latter duct Imeansy from said idle fuel duct to said pressure conducting means when said bypass duct means is open, thereby to increase the pressure in said pressure conducting means and to decrease the pressure in said idle fuel duct when said bypass -duct means is open, `and means for adjustably restricting said bypass duct means.

References Cited in the file of this patent UNITED STATES PATENTS 2,598,450 Shatf May 27, 1952 2,711,885 Moseley et al June 28, 1955 2,757,914 Ball Aug. 7, 1956 2,771,282 Olson et al Nov. 20, 1956 2,873,958 Dermond Feb. 17, 1959 2,882,027 Cook et al Apr. 14, 1959 2,969,965 Braun Jan. 31, 1961 

